1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, a method of producing the electrophotographic photosensitive member, a process cartridge, and an electrophotographic apparatus.
2. Description of the Related Art
In recent years, for the purpose of extending the life and improving image quality of an electrophotographic photosensitive member and increasing the processing speed of an electrophotographic apparatus, it has been desired to improve the mechanical durability (abrasion resistance) of an organic electrophotographic photosensitive member containing an organic photoconductive substance (hereinafter referred to as an “electrophotographic photosensitive member”). In order to improve the mechanical durability, according to one technique, a surface layer of an electrophotographic photosensitive member contains a polymer produced by polymerization of a compound having a polymerizable functional group.
Japanese Patent Laid-Open No. 2000-066425 discloses a technique of improving the abrasion resistance and electric potential stability of an electrophotographic photosensitive member by adding a polymer obtained by polymerizing a charge transporting compound having two or more chain-polymerizable functional groups to the surface layer of the electrophotographic photosensitive member. Japanese Patent Laid-Open No. 2010-156835 discloses a technique of improving the polymerizability of a charge transporting compound having a chain-polymerizable functional group (methacryloyloxy group) by adding a polymer obtained by polymerizing an electron transporting compound having two or more methacryloyloxy groups to the surface layer.
However, if a charge transporting compound having two or more chain-polymerizable functional groups is used, the charge transporting structure is easily distorted in chain polymerization. As a result, high electric potential stability is sometimes not achieved. Accordingly, Japanese Patent Laid-Open No. 2007-241140 discloses a technique of adding, to the surface layer, a polymer obtained by polymerizing a composition including a charge transporting compound having a single chain-polymerizable functional group and a compound that has three or more chain-polymerizable functional groups and that does not have a charge transporting structure. Japanese Patent Laid-Open No. 2009-015306 discloses a technique of achieving high electric potential stability by using a charge transporting compound which has a single chain-polymerizable functional group and in which an alkylene group is inserted between the chain-polymerizable functional group and a charge transporting structure.
However, the following has been found from studies conducted by the inventors of the present invention. That is, in the charge transporting compound having a single chain-polymerizable functional group disclosed in Japanese Patent Laid-Open Nos. 2007-241140 and 2009-015306, the ratio of a chain-polymerizable functional group that contributes to a chain polymerization reaction in one molecule is low, and the probability that a polymerization reaction does not proceed is higher in the charge transporting compound having a single chain-polymerizable functional group than in a charge transporting compound having two or more chain-polymerizable functional groups. Therefore, the residual potential tends to increase.